Acetylene gas, C2H2, is used as a fuel in welding torches. How many acetylene molecules are in a cylinder that delivers 1400 L of acetylene at STP?

375.8 × 10²³ molecules

Explanation:

Given data:

Number of molecules of acetylene = ?

Volume of cylinder = 1400 L

Temperature = standard = 273.15 K

Pressure = standard = 1 atm

Solution:

The given problem will be solve by using general gas equation,

PV = nRT

P= Pressure

V = volume

n = number of moles

R = general gas constant = 0.0821 atm.L/ mol.K  

T = temperature in kelvin

PV = nRT

1 atm × 1400 L = n ×  0.0821 atm.L/ mol.K    × 273.15 K

1400 L.atm = n × 22.43  atm.L/ mol

n = 1400 L.atm / 22.43  atm.L/ mol

n = 62.4 mol

1 mole contain 6.022 × 10²³ molecules

62.4 mol × 6.022 × 10²³ molecules / 1 mol

375.8 × 10²³ molecules